FortiGuard category-based DNS domain filtering

The FortiGate must have a FortiGuard Web Filter license to use FortiGuard Category Based Filter.

You can use the FortiGuard category-based DNS Domain Filter to inspect DNS traffic. This makes use of FortiGuard's continually updated domain rating database for more reliable protection.

To configure FortiGuard category-based DNS Domain Filter by GUI:

1. Go to Security Profiles > DNS Filter and edit or create a DNS Filter.
2. Enable FortiGuard Category Based Filter.
3. Select the category and then select Allow, Monitor, or Block for that category.

   

4. If you select Block, there are two options:
   • Redirect Portal IP. If the DNS query domain will be blocked, FortiGate will use portal IP to replace the resolved IP in DNS response packet. You can use the default portal IP 208.91.112.55 or click Specify to enter another portal IP.
   • Block. Blocked DNS query has no response return and the DNS query client will timeout.

   

To configure FortiGuard category-based DNS Domain Filter by CLI:

config dnsfilter profile
   edit "demo"
      set comment ''
      config domain-filter
         unset domain-filter-table
      end
      config ftgd-dns
         set options error-allow
         config filters  <<<==== FortiGuard Category Based Filter
             edit 2
                 set category 2
                 set action monitor
             next
             edit 7
                 set category 7
                 set action monitor
             next
            ...
             edit 22
                 set category 0
                 set action monitor
             next
         end
      end
      set log-all-domain enable
      set sdns-ftgd-err-log enable
      set sdns-domain-log enable
      set block-action redirect/block  <<<==== You can specify Block or Redirect 
      set block-botnet enable
      set safe-search enable
      set redirect-portal 93.184.216.34  <<<==== Specify Redirect portal-IP.
      set redirect-portal6 ::
      set youtube-restrict strict
   next
end

Sample

To see an example of how this works, from your internal network PC, use a command line tool such as dig or nslookup to do DNS query for some domains, for example:

#dig www.example.com
;; ->>HEADER<<- opcode: QUERY; status: NOERROR; id: 61252
;; Flags: qr rd ra; QUERY: 1; ANSWER: 1; AUTHORITY: 13; ADDITIONAL: 11

;; QUESTION SECTION:
;; www.example.com.             IN      A

;; ANSWER SECTION:
www.example.com.        17164   IN      A       93.184.216.34

;; AUTHORITY SECTION:
com.                    20027   IN      NS      h.gtld-servers.net.
com.                    20027   IN      NS      i.gtld-servers.net.
com.                    20027   IN      NS      f.gtld-servers.net.
com.                    20027   IN      NS      d.gtld-servers.net.
com.                    20027   IN      NS      j.gtld-servers.net.
com.                    20027   IN      NS      l.gtld-servers.net.
com.                    20027   IN      NS      e.gtld-servers.net.
com.                    20027   IN      NS      a.gtld-servers.net.
com.                    20027   IN      NS      k.gtld-servers.net.
com.                    20027   IN      NS      g.gtld-servers.net.
com.                    20027   IN      NS      m.gtld-servers.net.
com.                    20027   IN      NS      c.gtld-servers.net.
com.                    20027   IN      NS      b.gtld-servers.net.

;; ADDITIONAL SECTION:
a.gtld-servers.net.     21999   IN      A       192.5.6.30
a.gtld-servers.net.     21999   IN      AAAA    2001:503:a83e::2:30
b.gtld-servers.net.     21997   IN      A       192.33.14.30
b.gtld-servers.net.     21997   IN      AAAA    2001:503:231d::2:30
c.gtld-servers.net.     21987   IN      A       192.26.92.30
c.gtld-servers.net.     20929   IN      AAAA    2001:503:83eb::30
d.gtld-servers.net.     3340    IN      A       192.31.80.30
d.gtld-servers.net.     3340    IN      AAAA    2001:500:856e::30
e.gtld-servers.net.     19334   IN      A       192.12.94.30
e.gtld-servers.net.     19334   IN      AAAA    2001:502:1ca1::30
f.gtld-servers.net.     3340    IN      A       192.35.51.30

;; Received 509 B
;; Time 2019-04-05 09:39:33 PDT
;; From 172.16.95.16@53(UDP) in 3.8 ms

To check the DNS Filter log in the GUI:

1. Go to Log & Report > DNS Query to view the DNS traffic that just traverse the FortiGate and the FortiGuard rating for this domain name.

   

To check the DNS log in the CLI:

#execute log filter category utm-dns

# execute log display 
2 logs found.
2 logs returned.

1: date=2019-04-05 time=09:39:34 logid="1501054802" type="utm" subtype="dns" eventtype="dns-response" level="notice" vd="vdom1" eventtime=1554482373 policyid=1 sessionid=50868 srcip=10.1.100.18 srcport=34308 srcintf="port10" srcintfrole="undefined" dstip=172.16.95.16 dstport=53 dstintf="port9" dstintfrole="undefined" proto=17 profile="demo" xid=17647 qname="www.example.com" qtype="A" qtypeval=1 qclass="IN" ipaddr="93.184.216.34" msg="Domain is monitored" action="pass" cat=52 catdesc="Information Technology"

2: date=2019-04-05 time=09:39:34 logid="1500054000" type="utm" subtype="dns" eventtype="dns-query" level="information" vd="vdom1" eventtime=1554482373 policyid=1 sessionid=50868 srcip=10.1.100.18 srcport=34308 srcintf="port10" srcintfrole="undefined" dstip=172.16.95.16 dstport=53 dstintf="port9" dstintfrole="undefined" proto=17 profile="demo" xid=17647 qname="www.example.com" qtype="A" qtypeval=1 qclass="IN"